Chapter 2 General Principals of Traffic Signing * 07/16/96 Chapter 2 General Principals of Traffic Signing Sign Plan Design for At-Grade Intersections June 2017 *

MN MUTCD Minnesota Manual on Uniform Traffic Control Devices Minnesota develops and adopts a state MUTCD that is in substantial conformance with the Federal MUTCD The Minnesota MUTCD (MN MUTCD) was recently updated in July 2013 Chapter 2 of the MN MUTCD is dedicated to traffic signs.

MUTCD Text Headings Introduction The following definitions are taken from MN MUTCD Forward and Introduction: A statement of required, mandatory, or specifically prohibitive practice regarding a traffic control device. “Shall” is typically used. Are sometimes modified by

MUTCD Text Headings A statement of recommended, not mandatory, practice in typical situations, with deviations allowed if engineering judgement or engineering study indicates the deviation to be appropriate. “Should” is typically used. Are sometimes modified by

MUTCD Text Headings A statement of practice that is a permissive condition and carries no requirement or recommendation. May contain allowable modifications to a Standard or Guidance. “May” is typically used.

MUTCD Text Headings An informational statement that does not convey any degree of mandate, recommendation, authorization, prohibition, or enforceable condition. “Shall”, “should”, and “may” are not used in Support statements.

Traffic Engineering Manual The Traffic Engineering Manual (TEM) is issued and updated by the MnDOT Office of Traffic, Safety and Technology (OTST) The purpose of the TEM is to establish uniform guidelines and procedures, primarily for use by personnel at MnDOT See Chapter 4 of this Manual for a handout

Additional Signing Publications Found on the Signing Website: MnDOT Standard Signs Summary MnDOT Standard Signs and Markings Manual Freeway Signing Plan Design Course Manual Guide Sign Design Course Manual Signs 101 Course Manual A variety of reports and technical memorandums

Principles of Traffic Control Devices In order for signs to be effective, they should meet the following requirements: Fulfill a need Command attention Convey a clear, simple meaning Command respect from road users Give adequate time for proper response

Basic Considerations for the Installation of Signs In order to meet basic requirements, five considerations are employed: Design Placement Operation Maintenace Uniformity

Functional Classifications Regulatory Signs Warning Signs Guide Signs Primary Guide Signs Supplemental Guide Signs References: MN MUTCD 2A.5 TEM 6-4.03

Classification by Design Type Type A large breakaway guide, directional, or informational signs normally installed on mainline freeways, expressways, and occasionally on conventional highways They are supported on wide flange steel posts TEM 6-4.04 See Page 4-11

Classification by Design Type * 07/16/96 Classification by Design Type Department Classification by Sign Design Type Type C signs Primarily regulatory, warning, route marker assemblies, and auxiliaries, as found in the Standard Signs and Pavement Markings Manual Most common sign type Typically installed on driven U posts or square tube posts Around the year 1960, MnDOT did have a Type B sign. These signs were on one small wide flange post (W4X13 or W5X16) in concrete and Type C signs were installed on wood posts or U posts. Around 1962 MnDOT dropped the Type B signs and installed only Type C signs on U posts or X posts (two U posts back to back). *

Classification by Design Type * 07/16/96 Classification by Design Type Department Classification by Sign Design Type Type D signs are the smaller guide, destination, or informational signs. *

Classification by Design Type * 07/16/96 Classification by Design Type Department Classification by Sign Design Type Type OH – mounted overhead sign support (no walkway or sign lighting) *

Classification by Design Type * 07/16/96 Classification by Design Type Department Classification by Sign Design Type OH – Sign Bridge *

Classification by Design Type * 07/16/96 Classification by Design Type Department Classification by Sign Design Type OH - bridge mounted (may or may not include walkway and sign lighting) *

Classification by Design Type * 07/16/96 Classification by Design Type Type EA signs are exit number panels attached with U-posts to Type A sign panels *

Classification by Design Type * 07/16/96 Classification by Design Type Type EO signs are exit number panels attached with U-posts to Type OH sign panel *

Classification by Design Type Sign Symbols Appendix

Elements of Sign Design Page 2-5 Elements of Sign Design Sign Lighting Generally, sign lighting is not needed Each district/division shall conduct a field review to determine if it is necessary to light overhead signs During the review, Sign viewing should be made with low-beam headlights Personnel unfamiliar with sign message should be part of review team

Support for Type C & D Signs Page 2-6 Support for Type C & D Signs Type C Sign Supports Ground-mounted signs spliced or single U-posts driven into subsoil Attached to a bridge railing utilizing O-posts Banded to traffic signal pedestals or mast arm poles Unsupported length and sign panel area determines number of U-posts and need for stringers and/or knee bracing

Support for Type C & D Signs Page 2-6 Support for Type C & D Signs Type C Sign Panels Sheet aluminum with direct applied retroreflectorized or screen processed legend Punching is specified in the Standard Signs and Pavement Markings Manual

Support for Type C & D Signs Page 2-6 Support for Type C & D Signs Type D Sign Supports Same as Type C signs but generally supporting greater sign panel area They may be affixed to a bridge railing, traffic signal mast arm, etc.

Support for Type C & D Signs Page 2-6 Support for Type C & D Signs Type D Sign Panels Same as for Type C signs but splice plates may be required as specified in the Standard Signs and Pavement Markings Manual

Lateral Offset General Information in MN MUTCD 2A.19 and TEM Chapter 6 Page 2-6 Lateral Offset General Information in MN MUTCD 2A.19 and TEM Chapter 6 Located as far as practical from edge of shoulder Take advantage of existing roadside barriers, structures, etc.

Lateral Offset Type C & D Signs (Urban)

Lateral Offset Type C & D Signs (Rural)

Lateral Offset Type C & D Signs (Sign Placement Detail)

Mounting Height and Vertical Clearance Type A Signs

Installation & Maintenance Practices Page 2-8 Installation & Maintenance Practices Sign Groupings Signs of different functional classification should not be mixed in a given installation This may not always be possible in urban areas, so a sign of major importance may be placed above a relatively small sign of routine or secondary significance, unless this could mislead/confuse drivers

Installation & Maintenance Practices 6-4.07 Installation & Maintenance Practices Spacing of Signs – General Signs in a series must be uniformly spaced so that "a driver traveling at normal speed has adequate time to make the proper response” (MN MUTCD, Section 1A-2). As a rule of thumb for guide signs, every one inch of capital letter text height is equivalent to 30 feet of legibility distance

Installation & Maintenance Practices Page 2-9 Installation & Maintenance Practices Spacing of Signs – Rural Areas Sign spacing in rural areas should not be less than the distance required to read each sign at the upper range of anticipated vehicle approach speeds Minimum recommended distances between signs of different purposes on rural highways in Figures 6.24A, 6.24B, 6.25, and 6.26 in the TEM (Chapter 4).

Installation & Maintenance Practices Page 2-9 Installation & Maintenance Practices Spacing of Signs – Rural Areas Sign spacing in rural areas should not be less than the distance required to read each sign at the upper range of anticipated vehicle approach speeds Minimum recommended distances between signs of different purposes on rural highways in Figures 6.24A, 6.24B, 6.25, and 6.26 in the TEM (Chapter 4).

Installation & Maintenance Practices Page 2-9 Installation & Maintenance Practices Spacing of Signs – Urban Areas In urban areas with speed limits of 35 mph or less, the minimum distance between signs is 100 feet For 40 mph or greater, this distance is 150 feet

Installation & Maintenance Practices Spacing of Signs – Rural Areas Double Signing: If spacing approaches the minimum desirable distance, double signing may be utilized

Installation & Maintenance Practices Sign Installation Practice Windloading All ground-mounted and overhead signs shall be designed for a 50-year mean occurrence interval, which results in 90 mph wind speeds for Minnesota

Installation & Maintenance Practices Page 2-9 TEM 6-4.08 Installation & Maintenance Practices Sign Installation Practice A-Frame & U-Post Mountings Assuming an average distance of 10 feet from the bottom of the sign panel to the ground line, the correct sign structure design and post spacing can be determined by using the charts in Charts 6-2 and 6-3

Installation & Maintenance Practices 6-4.08 Installation & Maintenance Practices Sign Installation Practice A-Frame & U-Post Mountings Determine the total length of the sign panel Determine the height of the sign panel or add the heights of all of the individual sign panels to be mounted on the same sign structure Based upon these dimensions (in inches), determine the correct number of vertical U-Posts (riser posts) and knee braces from Chart 6.2

Installation & Maintenance Practices 6-4.08 Installation & Maintenance Practices Sign Installation Practice A-Frame & U-Post Mountings After determining the correct number of riser posts to be used for the sign structure, refer to http://www.dot.state.mn.us/trafficeng/signing/doc/canddsignground.pdf and the punch codes in the MnDOT Standard Signs Manual for the spacing from center to center of posts If there is no punch code or the sign structure is unique, then refer to Chart 6.3 in the TEM to determine riser post (center to center) spacing

Installation & Maintenance Practices Example Determine the total length (width) of the sign panel (below) In this example, the width of the sign is 66”

Installation & Maintenance Practices Example Then, determine the height of the sign panel or add the heights of all of the individual sign panels to be mounted on the same sign structure There is one sign in this example that is 36” high.

Installation & Maintenance Practices Sign Installation Practice A-Frame & U-Post Mountings After determining the correct number of riser posts to be used for the sign structure, refer to www.dot.state.mn.us/trafficeng/signing/doc/canddsignground.pdf and the punch codes in the MnDOT Standard Signs and Pavement Markings Manual For this example, there is not a punch code available since this is a non-standard sign

Installation & Maintenance Practices If there is no punch code or the sign structure is unique, then refer to Chart 6.3 in the TEM to determine riser post (center to center) spacing Since the panel width is 66”, the post spacing is 42” Also note from this same exhibit that a 72” sign also has post spacing of 42” In other words, this same structure could be used for a 66” or 72” sign

Installation & Maintenance Practices Sign Installation Practice A-Frame & U-Post Mountings Type C & D Sign Post Length Determination The length of the post is equal to the (1) Sign Panel Height, plus (2) the Mounting Height, plus (3), the U-channel Post Embedment

Installation & Maintenance Practices 6-4.08 Installation & Maintenance Practices Sign Installation Practice A-Frame & U-Post Mountings Post Lengths = (1) + (2) + (3) = 36” + 7’ + 3.5’ = 13.5’  14.0’ Add 2’ if on a slope.